Research Of The Preparation And Properties Of Rod-shaped Ferrites

Considering the effects of morphology and phase composition on ferrite magnetic properties, in this paper studies are made on preparation of rod-shaped spinel ferrite by chemical precipitation-toptactic method and impregnation-toptactic method and the formation processes of the rod-shaped Ni Fe2O4 by impregnation-toptactic method. By using homemade spinel ferrite as raw materials, the high purity rod-shaped W-type ferrite was prepared, and the influence of synthesis conditions on W-type ferrite magnetic properties was studied.Using α-Fe OOH and carbonyl polycrystalline iron fibers as raw materials, rod-shaped Ni Fe2O4 was prepared by chemical precipitation-toptactic method. The rod-shaped Ni Fe2O4 prepared by carbonyl polycrystalline iron fibers presents a high crystallinity, large length and aspect ratio and high content of various types of impurities. The Ni Fe2O4 ferrite prepared by carbonyl polycrystalline iron fibers presents lower value of Ms than those by α-Fe OOH because of its purity and magnetic properties of impurity. By using carbonyl polycrystalline iron fibers to replace the traditional acicular α-Fe OOH as raw materials and template, rod-shaped Ni Fe2O4 was prepared, which provides a new way to adjust the rod-shaped spinel ferrite morphology and size by adjusting material type and size.Using α-Fe OOH as raw material and template, rod-shaped and pure phase Zn Fe2O4 with a size of 0.4 to 1.4μm and aspect ratio of 2 to 15 were synthesized by chemical precipitation-toptactic method.Using α-Fe OOH and carbonyl polycrystalline iron fibers as raw material respectively, rod-shaped Ni Fe2O4 was prepared by the impregnation-toptactic reaction method. For α-Fe OOH as raw material, the length of prepared rod-shaped Ni Fe2O4 particle ranges from 0.3 to 0.6μm, and its aspect ratio is from 6 to 12, and it owns a saturation magnetization(Ms) of 30.74 emu/g and coercivity(Hc) of 386.54 Oe. For carbonyl polycrystalline iron fibers as raw material, a little amount of α-Fe2O3 is contained, and the particle length is about 20 μm, and aspect ratio is 4. They owns saturation Magnetization(Ms) of 36.67 emu/g and coercivity(Hc) of 194.40 Oe. Although the purity of Ni Fe2O4 prepared by using carbonyl poolycrystalline iron fibers as raw material is lower, the crystallinity is higher, and the lengthand aspect ratio of particle is larger. So compared with Ni Fe2O4 prepared from α-Fe OOH, the saturation magnetization has improved significantly. By using XRD, SEM, FT-IR and VSM techniques, the formation process of preparation of Ni Fe2O4 By impregnation-toptactic reaction method was studied thoroughly. The synthesis process of rod-shaped Ni Fe2O4 can be discribed as follow:“precursor(NH4NO3 and Ni(NO3)2 coated α-Fe OOH) ???????? ???????3222,,,, NHONNOOHOHα-Fe2O3 + Ni O ? Ni Fe2O4”and “precursor(NH4NO3、Ni(NO3)2 and Ni(OH)2 coated carbonyl polycrystalline ironfibers) ?????????? ????????32222,,,,, NHONNOOHOHOFe3O4 + Ni O ?????2O α-Fe2O3 + Ni O ? Ni Fe2O4”.Contrasting to the rod-shaped Ni Fe2O4 prepared from α-Fe OOH by the two methods. The purity of Ni Fe2O4 prepared by impregnation-toptactic method is relatively higher, but the length and aspect ratio of particle is relatively smaller, so the magnetic properties of Ni Fe2O4 prepared from α-Fe OOH by the two methods has no obvious difference. Contrasting to the rod-shaped Ni Fe2O4 prepared from carbonyl Polycrystalline iron fibers by the two methods. The rod-shaped Ni Fe2O4 by impregnation-toptactic method presents lower crystallinity, particle length and aspect ratio withless species impurities and lower content, which leads to a higher Ms(36.67 emu/g) than Ms(18.37 emu/g) of Ni Fe2O4 prepared by the chemical precipitation-toptactic method.For homemade rod-shaped Ni Fe2O4 as the raw material, Ni2-W-type ferrites prepared by chemical precipitation-toptactic method and impregnation-toptactic method show close packing hexagonal flake and irregular flake morphologies with Ms values of 56.40 and 59.15 emu/g and Hc values of 519.57 and 628.47 Oe. From the study of the influence ofthe main factors of the two methods on synthesis of Ni2-W magnetic energy, it is found that using impregnation-toptactic method a decrease of Ba/Fe(mol/mol) causes a gradual increase of Ms. An increase of p H value and a decrease of Ba/Ni(mol/mol) or an increase of the burning rate leads to an increase followed by a decrease of Ms. When Ba/Fe(mol/mol) is 1:12, Ba/Ni(mol/mol) is 1:1.8, p H is 10, roasting rate is 3℃/min, Ni2-W present relatively high Ms. Using chemical precipitation-toptactic method, Ba/Fe(mol/mol) had no obvious effect on Ms. An increase of p H value, or titration incubation time or burning rateleads to an increase followed by a decrease of Ms. When Ba/Fe(mol/mol) is 1:11, p H is 10, titration incubation time is 24 h, roasting rate is 3℃/min, Ni2-W presents relatively higher Ms.With homemade rod-shaped Zn Fe2O4 as the raw material, the Zn2-W-type ferrites synthesized by chemical precipitation-toptactic method and impregnation-toptactic method show close packing hexagonal flake and irregular flake morphologies with Ms of 63.50 and 63.14 emu/g and Hc of 450.16 and 504.50 Oe. The synthesis of coarse rod-shaped Zn2-W usingrod-shaped Zn Fe2O4 as raw material and template is feasible. From the study of the influence of the main factorsof two methods on synthesis of Zn2-W magnetic energy, it is found that for using impregnation-toptactic method, a decrease of Ba/Fe(mol/mol) and Ba/zinc(mol/mol) or an increase of the burning rate leads to an increase followed by a decrease of Ms. An increase of p H value leads to an increase followed by a decrease of Ms. When Ba/Fe(mol/mol) is 1:13, p H is 10, Ba/Ni(mol/mol) is 1:1.6, roasting rate is 3℃/min, Zn2-W presents relatively higher Ms. For using chemical precipitation-toptactic method, a decrease of Ba/Fe(mol/mol) or an increase of p H value leads to an decrease followed by a increase of Ms. An increase of titration incubation time or burning rateleads to an increase followed by a decrease of Ms. When p H is 9, Ba/Fe(mol/mol) is 1:12, titration incubation time is 24 h, roasting rate is 3℃/min, Zn2-W presents relatively higher Ms.Comparing with chemical precipitation-toptactic method, impregnation-toptactic method has some advantages in preparing ferrites, such as simple equipment, ease operation, cost saving, and ease realization of mass production.